I have heard of RX7's having the oil injection (OMP) removed/bypassed and running only MMO as a premix and doing great for many, many miles - that said, I would not do a total replacement.
Marvel itself, recommends replacing 25% of your total 2 cycle oil requirement to achieve your required fuel/oil ratio with MMO, just like when replacing sump oil. MMO after all, is designed as a supplement to oil, 2-cycle or 4-cycle, not a total replacement.